DNS_CLIENT_UPDT support is incomplete

I tried defining DNS_CLIENT_UPDT, but the compiler returned several warnings and an error when compiling IP_DNSC.c:

Error: 'dns_servers' is undeclared - I assume this is an array of DNS IP addresses, not 100% sure
Warning: implicit declaration of 'MEMCPY' - will lead to link error, probably needs to be change to IP_MEMCPY
Warning: impicit declaration of 'tk_yield' (a holdover from interniche) - will lead to link error, probably needs to be changed to OS_Yield
Warning: 'getsoa' declared static but never used - ok, there's only a function prototype, no actual function

Are DNS updates by the client not supported? If yes, then why not and why is this code in here?

This functionality is not documented and is therefore not meant to be used.

As you already mentioned, this is code that is a leftover from the original Interniche stack.
This code seems to be overseen during cleanup operations. At the moment our stack does not
support this feature and it is not planned to implement this feature the way it was.

I am getting more frustrated with and disappointed by embOS/IP.

If you feel that there is a problem with embOS/IP and the functionality that our stack has been designed for and that is documented to be
available for usage, please contact our support team and we will try to solve problems as soon as possible.